What might have motivated suspects Tamerland and Dzhokhar Tsarnaev in the Boston bombings? Simplistic answers – say, Islamic militancy or immigrant anger – may not suffice. Yet knowing such motives may help everyone act to prevent such attacks.

“Worldview: Islam. Personal priority: career and money,” wrote Dzhokhar.

“I don’t have a single American friend, I don’t understand them,” said the older brother, Tamerlan.

Their uncle, Ruslan Tsarni, told reporters: “Being losers, not being able to settle themselves and thereby just hating everyone else who did.”

The list of possible reasons goes on as more information about them is revealed – perhaps even by an injured Dzhokhar from his hospital bed.

The public desire for a simple explanation is driven by a desire for simple solutions to prevent a similar attack. After almost every mass killing – Boston, Newtown, Aurora, 9/11, etc. – the public fear of a recurrence pushes the drive for quick remedies, especially from government. Yet too often elected leaders and law enforcement respond hastily with simplistic or even wrong preventive measures.

Remember the five-color “threat alert system” from the Department of Homeland Security? It’s gone. The invasion of Iraq, too, looks like a misguided response to 9/11. Airport security checks are being constantly revised.

Pinning down the motives of an attacker can be an impossible task, making prevention more complex. And merely adding more “hard” defenses – such as armed teachers in schools, drone attacks on terrorists, or bag checks at public events like a marathon – may not be enough without dealing with motives. Background checks for gun buyers, however, at least begins to deal with motives – weeding out those not stable or trustworthy enough to own a gun.

As the final capture of the suspected Boston bombers shows, government needs everyone to be alert in helping solve and perhaps prevent a mass crime. The bombers had been filmed by private citizens, for example, and Dzhokhar was discovered in a boat by an alert resident of Watertown, Mass.

Such actions speak to a deeper need to be aware of others – mainly troubled young men – who may act or speak in a way that could lead to violence. Would-be killers can be stopped if only one person perceives something wrong and works to counteract it.

This isn’t always easy. Being alert to evil motives takes discernment as well as well-meaning and sensitive outreach. How many mass killings have been prevented by wise intervention? We may never know. But what if someone had been able to reach Tamerlan and Dzhokhar Tsarnaev before they descended into darkness?

As more potential motives in this case become clear, each one is a cause for people to see if there are others in their lives who might have similar motives. “Be not overcome of evil, but overcome evil with good,” Paul wrote in Romans.

Or as poet Wordsworth reminds us: “The best portion of a good man’s life: his little, nameless, unremembered acts of kindness and of love.”